The applicants received funding for one year for a project directed towards the development of computerized, non-invasive measurement system designed to evaluate motor disorders in a clinical neurological setting. A method was developed that operationally defines two human motor systems, referred to as the feed-forward based volitional motor system and the feed back based reflexive motor system. The measurement system records and identifies abnormalities in each motor subsystem and in the coordination of the subsystems. While older methods measure either the volitional or reflexive system, the current method attempts to evaluate both as well as the coordination between the two systems. The Phase II proposal focuses on the development of a safe and automated testing platform to quantify motor control abnormalities. One goal is to complete the development of the platform to a stage ready for commercialization and the second goal is the continued quantitative evaluation of Parkinson's disease and other movement disorders. The main finding in this effort is that when sinusoidal visually guided wrist tracking movements are performed, which are perturbed by torque transients out of phase throughout the movement, both the long latency stretch reflex and volitional EMG can be assessed at different phases in the tracking. Reflex modulation during tracking differed significantly between Parkinson's patients and normal subjects in both wrist flexor and extensor muscles. In the Parkinson's group, there was an increased reflexivity during tracking phases in which the muscle was stretched. As a consequence, this increased reflex activity interfered with the volitional activity. No differences in unperturbed volitional EMG modulation were observed between the two groups, demonstrating that the changes in reflex modulation are due to disordered volitional modulation and/or changes alpha motorneuronal excitability.